There is a itoa conversion issue in QuicStreamSequencerBuffer which converts a unsigned int to signed int.

string RangeDebugString(QuicStreamOffset start, QuicStreamOffset end) {
  return string("[") + base::IntToString(start) + ", " +
         base::IntToString(end) + ") ";
}

https://code.google.com/p/chromium/codesearch#chromium/src/net/quic/quic_stream_sequencer_buffer.cc&l=19

This effects the debug string for QUIC_OVERLAPPING_STREAM_FRAME, which supposed to be something like this:
Beginning of received data overlaps with buffered data.
New frame range [1024, 2048) 
Currently received frames: 
Current gaps: [1447, MAX_QUIC_STREAM_OFFSET) 

However it prints out as this:
Beginning of received data overlaps with buffered data.
New frame range [1024, 2048) 
Currently received frames: 
Current gaps: [1447, -1)